This invention relates to the manufacture of gun ammunition (cartridges) which include a case having a closed end which houses a primer and an open end, gun powder disposed within the case, and a projectile secured in the open end of the case.
Gun ammunition, known also as cartridges, are of standardized dimensions for a given caliber gun. These standards are set by the Sporting Arms and Ammunition Manufacturers Institute (SAAMI). For those guns which operate in the automatic or semi-automatic mode, the overall length (OAL) of the cartridge is critical to the successful operation of the mechanism which feeds the cartridge from a magazine into the breech of the gun. Further, maximization of impact energy of the projectile upon striking a target dictates that the projectile be of maximum weight. Any given projectile desirably travels from the gun muzzle to a target with the longitudinal centerline of the projectile aligned with the trajectory of the projectile, that is, the projectile exhibits stability of flight from the gun muzzle to its target. A projectile can be overstabilized or understabilized. Among the many factors which affect the stability of a projectile in flight are the spin effects created by firing the projectile from a rifled gun barrel, precession (i.e. yaw about the center of gravity of the projectile), nutation (another movement inside the precession), and wind effect. The wind effect may be reduced toward a minimum by making the projectile heavier, such as by fabricating the projectile from a heavy metal such as tungsten. Increasing the length of the projectile also can increase the overall weight of the projectile (for a given caliber).
As noted, the size (geometry), including the length of a cartridge case is established by the standards set in the industry so that any given caliber ammunition cartridge will be received within the firing chamber of any gun of such given caliber. Thus, if one chooses to increase the length of the projectile of such caliber cartridge, and also desires to maintain the OAL of the cartridge within a given range, the only place the extra length of projectile can go is within the case. Thus, the "extra" length of the projectile takes up space within the interior of the case which normally would be available for gun powder. In order for the heavier projectile to be fired from the gun at a given muzzle velocity, it is required that the gun powder be chosen to accommodate the heavier projectile, both from the standpoint of the increased weight of the projectile and the fact that there is less volume within the case for gun powder. In any event, it becomes desirable that there be a maximum amount of gun powder loaded into the case (along with the trailing end of the projectile).
In the manufacture of gun ammunition, it is common practice to support the case in an upright position with its open end facing upwardly, introduce a measured quantity of gun powder into the case, and thereafter insert the trailing end of a projectile into the open end of the case. Most commonly, the open end of the case is crimped about the circumference of the projectile to anchor the projectile in the case. This prior art practice is acceptable where the length of the projectile is such that very little, of any, of the length of the projectile projects into the interior of the case beyond the inboard terminal end of the neck of the case. But where any material portion of the length of the projectile projects into the interior of the case beyond the inboard terminal end of the neck of the case, there is formed an annular space between the outer surface of the projectile and the inner surface of the case. When employing conventional methods for inserting projectiles into cases, this annular space is devoid of gun powder. This factor exacerbates the problems of choice of the type of gun powder and the volume of gun powder which can be added to the case.
It is of importance to note that the individual particles of a commercial gun powder are deliberately sized and of a geometry as will produce a given result when ignited within a cartridge case. Specifically, the individual particles of a given gun powder may be flakes, balls, non-perforated grain (cylindrical), single perforated grain (tubular), or multi-perforated grain, for example. Each shape is designed to provide a given burn rate for each powder particle, which in turn develops a collective distinctive gas pressure curve for each type of gun powder. This burn rate and resulting gas pressure curve are critical for developing a given muzzle velocity for a given projectile from a gun. Any destruction, even partial, of the shape of particles of the gun powder will alter the gas pressure curve of a given charge of the gun powder. Accordingly, it is not permissible when loading a projectile in a case, that the projectile be forced into contact with the powder particles such as will even partially destroy the shape of the particles. For this reason, when inserting a projectile into a case such that the trailing end of the projectile projects into the case beyond the inboard terminal end of the neck of the case, it is not permissible to allow the trailing end of the projectile to contact the gun powder, which is already in the case, with a force which will destroy the shape of the gun powder particles. Thus, it will be recognized that it is not permissible to urge the projectile into contact with the gun powder in the case to the extent that the projectile displaces the gun powder radially outwardly and upwardly of and within the case in an attempt to cause the gun powder to be displaced into an annular space between the projectile and the case. Heretofore, this factor has acted as a limit to the permissible length of a projectile for a given caliber cartridge and has limited full utilization of the volume available within the case for receiving gun powder when using longer projectiles.